Batch File Programming - Part One
Batch File Programming - Part Two
____________________________________________________________
GUIDE TO (mostly) HARMLESS HACKING
Microsoft-only version Number 2
Hacking with Win95/NT: Batch File Programming
____________________________________________________________
by KeyDet89
I figured that, after all of the Happy Hacker Digests
and Guides To (mostly) Harmless Hacking that have
dealt with shell programming, something for Win95 and
NT needed to be addressed.
***************************************************
Newbie Note: A good resource for batch files is to go to
you local library and look up back issues of PC Magazine.
The older editions, even those published after Win95 came
out, list several useful batch files that you can use
or modify for your own use. WindowsNT Magazine has had
several good articles on scripting languages for NT.
Other excellent sources of information include books from
the library and used bookstores.
Also, visit the alt.msdos.batch newsgroup. If you can't
access newsgroups from your ISP, use your browser to
visit DejaNews at http://www.dejanews.com/. Or visit
any of the sites listed at the end of this file.
***************************************************
Let's get started. First, keep in mind that batch files
are just series of programs that you would like executed.
The files are made up of commands that already reside on
your machine. If you have several commands that type over
and over, each with specific switches and parameters, you
may want to put them into a batch file. Batch files can
also be used the way aliases are on Un*x...written properly,
you can launch a program from the command line without
having to type it out each time.
A word about editors: You already have two suitable text
editors on your computer...DOS edit, and Notepad. Edit
is fairly simple to use, but you may not be used to it.
Notepad is also easy to use, just remember to save your files
with the correct ".bat" extension so that they will be
recognized as batch files by the command processor.
***************************************************
Newbie Note: Most of the commands that you will want
to run from batch files will be command line programs.
Check out your windows\command directory to see what
is available. Don't hesitate to look for DOS or Win95
command line programs on the Internet.
***************************************************
STEP 1 -- "Hello, World"
The first program we will write is the obligatory "Hello World"
program that accompanies every programming language. Simply
save a file called "hello.bat" with the following text:
echo Hello, World!
Now, if you type "hello" at the prompt, you will see the "echo"
line printed at the prompt, then the line "Hello, World!" on the
line below it. To suppress the commands at the prompt, add the
line:
@echo off
as the first line of the file. Now rerun the file.
STEP 2 -- Arguments
Now, let's personalize our program a bit. Change the second line
to:
echo Hello, %1
and run the program by typing:
c:\>hello Johnny
Now we've added arguments, as denoted by the "%1". This refers to
the first argument that is sent to the file. We can send multiple
arguments. To demonstrate, open a file called "args.bat" and type
in the following lines:
@echo off
echo ARGS: %1 %2 %3 %4
echo REV: %4 %3 %2 %1
echo MIXED: %2 %1 %4 %3
Now run the file with at least two arguments (you can use more and
examine the output):
c:\>args hello steve dog rain
STEP 3 -- Redirection
When programming in most languages, there are three references that
you need to be aware of: standard input (STDIN - usually the
keyboard), standard output (STDOUT - the screen), and standard
error (STDERR - also the screen). However, you may not want the
output to go to the screen, you may want it stored in a file. Well,
we can do this fairly easily with something called redirection.
How does this work? Well, when you type in something like:
c:\>attrib /?
to find out what the attrib (attribute) command does, and how
it is used, you see a lot of information on the screen. Try doing
the same thing with the "net" command under Win95, and the info
seems to disappear off the screen! So to send the output of the
command to a file, simply add the greater-than sign and a file
name to the command:
c:\>net /? > net.txt
If you want to add or append information to an already existing
file, use the double-greater-than symbol:
c:\>net view /? >> net.txt
****************************************************
Cool Trick To Try: I won't be covering HTML programming here,
but here is something to try. There are basic commands that
every web page has...these are the tags that are that are used
to designate the header, title, change colors or fonts, etc.
Write a batch file that takes the output of series of commands,
such as "net", "net view", "net use", "net user", and "net time"
and puts them in an HTML file. That way, you can post it on
the web. You may even go so far as to include links to examples,
etc.
****************************************************
STEP 4 -- Autoexec.bat
Now is a good time for a word on the King of All Batch Files,
the autoexec.bat file. This is the file that is used by DOS
at boot up, and exists for DOS and Win95 (Win3.1 runs on top of
DOS, and is called from the autoexec.bat file). Use the
autoexec.bat file "to set the characteristics of your devices,
customize the information that MS-DOS displays, and start
memory-resident programs and other applications" (from the
MS-DOS User Guide). Really? Well, given that, you can do all
sorts of interesting things with this file...or any other batch
file.
Note on NT: NT does not use the autoexec.bat file, but there
is a registry key that when set, will enable the parsing of
the autoexec.bat file, reportedly for environment variables.
Gee, I wonder what else it will do...
*****************************************************
Evil Genius Tip: Take a look at the prompt command by typing:
c:\>prompt /?
Play around with different settings. Typing the command to
change the prompt at the current command prompt will change
it for that session...adding the command to the autoexec.bat
file will change if for all sessions.
*****************************************************
STEP 5 -- Aliases
You'll notice that when you type:
c:\>notepad somefile.txt
Notepad opens with the file, and in the DOS window, you get
you command prompt back. So if you want a quick way to open
the text files, create a small batch file called "np.bat", with
the lines:
@echo off
notepad %1
Now all you have to do is type "np" and the file name.
****************************************************
Evil Genius Trick: Here's a handy little way to create a
mini-syslog daemon of your very own...or someone elses.
Create a file called "file.log", or whatever, on the
target computer, in the Windows directory.
HINT: Investigate the "attrib" command, paying particular
attention to the "h" option.
Now, create a batch file that will make entries to file.log.
You might want to have something printed, or just the file
that was opened.
Next, click Start -> Help, and type in "associating" and
display the help on "file types with programs". Change
the associations for ".txt" files to point to your batch
file, and make sure that the last line reads:
notepad %1
If your friend uses Microsoft Word a lot, make the
appropriate changes there, too.
****************************************************
****************************************************
Neat Trick Tip: If you like the Un*x commands, but don't
want to fool with downloading them, write you own. Create
a batch file called "ls.bat" and use the "dir" commands to
customize the display. Start with:
@echo off
dir %1
Make sure to see what switches are available for the dir
command...
****************************************************
STEP 6 -- Information Gathering
There are several commands that can be used to gather
information, especially on a networked computer. These
commands can be used to gather information for diagnostic
purposes, as well as being used for other insidious
purposes (no Evil Genius Tips here, I'll leave it up to
your imagination). Start by running the following commands
on your machine while connected to a network or to the
Internet:
nbtstat -c
nbtstat -n
netstat -an
net user (NT only)
net use/config/time/view
arp -a
When you begin to see the type of information that is
available, tailor the commands to your needs, and put
them in a batch file, redirecting the output to a log file
of some sort.
STEP 7 -- More Stuff
I have gathered together some sites that provide more
detailed information on batch file programming. These sources
range all the way from examples to tutorials to post-graduate
theses...so take a look...
BATCH FILE PROGRAMMING SITES
ftp://garbo.uwasa.fi/pc/ts/tsbat53.zip
http://gearbox.maem.umr.edu/~batch/
http://www.nc5.infi.net/~wtnewton/batch/index.html
http://purl.oclc.org/net/dirk/batcoll.all
http://purl.oclc.org/net/dirk/batvirus.all
http://www.deltaelectronics.com/tglbatch/
___________________________________________________________
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Hacking, please email hacker@techbroker.com with message "subscribe
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Copyright 1998 KeyDet89 <keydet89@yahoo.com>. You may forward or post this
GUIDE TO (mostly) HARMLESS HACKING on your Web site as long as you leave
this notice at the end.
___________________________________________________________
Carolyn Meinel
M/B Research -- The Technology Brokers
http://techbroker.com/
____________________________________________________________
GUIDE TO (mostly) HARMLESS HACKING
Microsoft-only version Number 3
Hacking with Win95/NT: Batch File Programming
____________________________________________________________
by Nezah
We've learned what a batch file is and how to write them. Now it's
time to get all that batch files can bring us. Lets start.
1.- The IF command
It's easy to find out what it is for. The if command evaluates an
a condition and, in case of true result, it executes a command. There are
three ways to use IF. The different sintax are these:
IF [NOT] EXIST file command
IF [NOT] string1==string2 command
IF [NOT] ERRORLEVEL number command
Where command is the order (only one) you want to execute. The
NOT word is optional, and it makes the condition inverese. Lets see one
by one.
**IF [NOT] EXIST file command.
What it does is to find out if there is or not a file. If the file
exist (or not, if the NOT word is typed) then the command is executed.
Otherwise, the command is ignored.
=========================================================
TIP: Maybe you don't want to verify a file, but a drive or a directory. In
this case, you have to look for the "file" NULL, that is present in
any directory. For example, if you want to verify the c:\nezah
directory, type this:
IF EXIST C:\NEZAH\NULL command
To test if a disquette is in, type this:
IF EXIST A:\NULL command
=========================================================
**IF [NOT] string1==string2 command
Compares the two strings string1 and string2. In case that every
character is equal in both (case sensitive and blank spaces ignored), the
command is executed.
It is useful to play with the parameters (read GTmHH Micro$oft 2).
Note now that, when a parameter call is found (for example, %1), DOS replaces
it for the text of the parameter, no matter where it is. For example, if %1
is Happy, when DOS finds:
00%100
replaces it for:
00Happy00
The same with "%1" ---> "Happy"
" %1 " ---> " Happy "
============================================================================
NOTE: If a parameter does not exist, DOS replaces it with a blank space or
just with nothing (in W95 OSR2 is nothing). To avoid lose control of
the program, is useful to put every string into quotes. So, for example,
if you want to see if a parameter is present, type:
IF "%1"==" " command ---> DOS 6.x
IF "%1"=="" command ---> In W95 is empty string ""
In any other cases, quotes are not needed and strings are compared
normally.
=======================================================
**IF [NOT] ERRORLEVEL number command
This evaluates the last errorlevel number present. Errorlevels are
generated by programs to inform about the way they finished their execution.
For example, format returns errorlevel 3 when is Ctrl-C is pressed, and
errorlevel 0 when it finish normally. Not all the programs return errorlevels,
and errorlevels are lost when another program is runned.
This is the most useful feature of IF command. We'll explain it later,
with the CHOICE command.
2.- Labels and GOTO command.
Labels are used to identify a line of the batch file. The way to
put a label inside a .bat progam is simply to put : before the label name.
For example, to create the "example" label, do this:
:example
And that's all.
Labels get useful when you use the order GOTO. GOTO simply goes to
the labeled line you want. For example, to go to the :example label just type:
GOTO :example
That makes the execution of the .bat file continue above that line,
no matter if it was far below the current line or before it.
======================================================
NOTE: The label does not defines a function (like in programming languajes).
It makes the execution continue below the :label line.
When, in normal execution, a :label line is found, it is ignored. The
only use of lables is with the order GOTO.
======================================================
======================================================
TIP: You can create a :end label at the end of the file, so that, whenever
you want to finish the program, you just have to type "GOTO :end".
======================================================
======================================================
TIP: Remember that, in the IF sentence, only was allowed one command.
This sucks, I know. But now, you can create a label and make this
only one command be GOTO :label. Then, in this :label you can have
as many commands as you want, and finish the execution or return to
the program point you wanted with :end or :new_label
======================================================
3.- CHOICE
Now we're ready to get the maximum power from the choice command.
We saw before that errorlevels are some kind'a number that programs returned
and so on. That was not very useful, I know, but for the choice program.
The choice program takes a letter from the keyboard and returns an
errorlevel in consecuence of the key pressed. The sintax is:
CHOICE [text] [/C[:]keys] [/S] [/N] [/T[:]key,secs]
Text is no more than the text to show when choice is runned.
/C:keys Defines the possibles keys to be pressed. If no option is
present, Y/N are the keys. For example:
CHOICE /C:ABCD
Defines A,B,C,D as possible keys.
If you press a not defined key, you'll hear a beep and will
continue as if nothing was pressed.
/S Makes CHOICE case sensitive. By default, Z is equal to z for
choice. With /S flag present, Z and z are different.
/N Choice shows the possible keys into brackets when is called.
With the /N flag present, it does not, so that only the text
you typed (if so) is shown.
/T:key,secs defines a key that is taken as default when secs seconds
are passed. For example:
CHOICE Chose drive /C:AC /T:C,5
Shows the message "Chose drive [A,C]" (without quotes) and,
if no key pressed, passed 5 seconds, choses C.
**Way it works
Now we know how to make the CHOICE sentence. Lets see what happens
when CHOICE runs. It returns an errorlevel number corresponding to the key
position in the /C flag. What???. Well, lets se an example:
CHOICE /C:ABCD
|||L____> D gives errorlevel 5
||L_____> C gives errorlevel 4
|L______> B gives errorlevel 3
L_______> A gives errorlevel 1
Now you see that the errorlevel number depends on nothing but the
position of the key that you gave to CHOICE. That is, when you type
CHOICE /C:2567
Pressing 2, CHOICE will give us errorlevel 1, 5 will give
errorlevel 2, 6 errorlevel 3 and 7 errorlevel 4.
Lets see now what to do with errorlevel. If you remember the IF
section, there was an:
IF [NOT] ERRORLEVEL number command
This evaluates the current errorlevel number. If condition is true
the command is executed.
===================================================
IMPORTANT NOTE: The evaluation of an errorlevel is true when the current
errorlevel is equal OR HIGHER than the number compared. That means
that, in:
IF ERRORLEVEL 3 GOTO :label
The condition is true for errorlevel 3, 4, 5... and every errorlevel
equal or greater than 3.
===================================================
To clarify this, read the next example.
@ECHO OFF
ECHO.
ECHO 1.- Runs Windoze 3.11
ECHO 2.- Runs Dosshell
ECHO 3.- Runs Quake
ECHO X.- Exit program
ECHO.
CHOICE "Choose your option " /C:123x /N
IF ERRORLEVEL 4 GOTO end
IF ERRORLEVEL 3 c:\quake\quake -listen 16
IF ERRORLEVEL 2 dosshell
IF ERRORLEVEL 1 win
:end
This is a complete batch program. Lets analyze it.
First line turns ECHO off: the command lines inside the program will
not be shown.
Second line prints an empty line (like pressing RETURN).
Lines 3 to 7 prints the messages for the program.
Line 8 is choice. This will show you only the text (because of the
/N flag) and will only allow you to press 1,2,3,4 or x key. It is case
unsensitive (no /S flag given). Note that the text is into quotes. This is
to make CHOICE respect the blank space at the end. Quotes will not be shown,
and are not required. If you unuse quotes, CHOICE will not print the blank
spaces of the begining or the end of the text.
Lines 9 to 12 evaluates the errorlevel. Note that:
Only numbers are evaluated. No X letter is writen.
It is in decreasing order. That is because the evaluation is
true if the current errorlevel is equal or higher. So
if I start with errorlevel 1, and errorlevel 4 (an
X) is pressed, I will execute the command anyway.
The execution of the batch file continues after the program
you called is runned. So, if the program returns
errorlevels, you may get an error. Commands CLS,
CD and DIR doesn't reset the current errorlevel, and
other DOS commands returns their own errorlevels. So,
when you call a DOS order, is better to make a GOTO
anyway, to avoid stupid errors.
In the first IF ERRORLEVEL... the goto order does not have
: before the label name. This is because they are
not required in the goto call.
Line 13 is the label end. When you call it, the programs finish.
4.- The command FOR
Now we'll se how to make a batch file smaller. The for order is not
very useful, but sometimes is exactly what you need. So lets see it.
The FOR command makes a "variable" change it's value between the
posibilities you gave it, and executes a command every time it changes. The
sintax is that:
FOR %%A IN (list of values) DO command
Here %%A is the name of the variable. (list of values) is just
the list of values (easy, uh?) between which will change the variable %%A.
The different values are separed by a blank space, and are only considered
as strings.
=======================================================
Programes NOTE: The variables are not true variables. They are only valid
in the FOR command, and will lose any meaning after FOR is finished.
=======================================================
Lets see an example to explain it:
FOR %%B IN (Hello Happy Hacker) DO ECHO %%B
This will make the variable %%B change it's value. First time will
be Hello. Second time Happy, and third Hacker. Every time the %%B value is
changed, the command after the DO word (ECHO %%B in our example) is executed.
So this line in a batch file will print in our screns:
Hello Happy Hacker
There is something more to say about FOR. I have never tried it, but
I read that: when you give FOR a wildcard, it will take care to substitute it
for every existing filename that fits the wildcard. That is that, if you have
FOR %%A in (AUTO*.BAT) DO copy %%A c:\backup
the copy command will recive every time complete file names and no wildcards.
This will execute, for example:
copy AUTOEXEC.BAT c:\backup
copy AUTODOS.BAT c:\backup
copy AUTODOS7.BAT c:\backup
And not something like:
copy AUTO*.BAT c:\backup.
This may be useful with programs with no wildcards alowed, like the
expand command, that expand a compressed file.
5.- Other orders.
**REM and the commets.
To comment a complete line, you should use REM at the begining of it.
You can also use : before tha line. But this will make the line a label, I
conseder this quite rough. It's up to you.
========================================================
Newbie note: A comment is something ignored in the execution of the program.
Every programming language has at least one way to make comments.
This is extremely useful to make your program easier to read to other
people and to yourself in future.
========================================================
**CALL
When you call an .exe of a .com or a DOS command inside a batch file,
after the execution of this program, the .bat file will continue at the point
it was before. But this is not this way when you call a .bat file. I you run
another .bat file inside another, the second one will take control and won't
return it after is finished. To run a .bat file inside another and after
continue the program that called the second, we have to use the order CALL.
That's what CALL does: execute
